You probably know someone—a relative, friend, coworker—who has dealt with cancer. Some of us have gotten the terrifying diagnosis ourselves. Cancer gets top billing on the news, whether it’s about promising new therapies, scary statistics or debates about screenings. Questions about it may pop into your head randomly: Is this cigarette giving me cancer? Will eating these vegetables protect me? My mom had it; when will it strike me too? Cancer can seem like a mysterious disease, especially because it’s a condition that attacks from within our own cells.

It’s time to demystify cancer. “The word cancer frightens all of us,” says Stephen Brewer, M.D., medical director of Canyon Ranch in Tucson. “However, understanding many of the causes of cancer and finding ways to prevent it from reoccurring are certainly a beginning in decreasing our fears of this disease.”

Let’s start by putting to rest some common misconceptions. “First, cancer is not one disease,” Dr. Brewer says. It’s actually more than 100 different conditions. Nor is cancer a death sentence; the truth is that more of us than ever are surviving a cancer diagnosis. Each year, 1.7 million Americans get a new cancer diagnosis, and 580,000 die from the disease. But the survivor numbers keep growing: There are now nearly 14 million American cancer survivors, a number that’s expected to grow to 18 million by 2022.

There are also cancers that are so benign that some scientists believe we shouldn’t even call them cancer (more on that below). Other types are so slow-growing that they’ll probably never hurt you. Many others are highly treatable; they can be either cured or kept at bay for years, even indefinitely.

A healthy lifestyle—one that nurtures your body, mind and spirit—may help prevent many cancers, as well as reduce your risk of recurrence if you do develop it. And if you are diagnosed with cancer, a healthy lifestyle is key to living your best and most vibrant life before, during and after treatment.

The hallmark of cancer is uncontrolled cell growth: Abnormal cells either don’t die when they’re supposed to or they continue to multiply when they shouldn’t. “Cells divide to produce new cells,” explains Stephen Brewer, M.D., medical director at Canyon Ranch in Tucson. When things work normally, old or damaged cells are killed off and new ones replace them. Sometimes, though, the genetic material of the cell—the DNA—is damaged or changed and the cell continues to divide, eluding the body’s biological process that turns off cell growth.

These extra cells may then become a tumor, which can be benign (non-cancerous) or malignant (cancerous). Cancer cells may invade nearby tissues or spread to other parts of the body through the blood or lymph systems. When a cancer moves from one organ to others the process is called metastasis.

What Causes Cancer?

That out-of-control cell growth can happen as the result of a variety of factors, including inherited genetic mutations and excess hormones (in women, too much estrogen in particular). It may surprise you to learn that, at this time, researchers believe that only five to 10 percent of cancers are inherited; that means that regardless of whether someone in your family has had cancer, you still have a lot of control over your risk. Cancer can also be caused by cancer-causing agents (called carcinogens) that you’ve been exposed to, like tobacco smoke, UV rays from the sun, toxic chemicals and certain viruses and bacteria.

You’re probably aware that your weight, diet and exercise habits and stress level may also contribute to your cancer risk. “Your body is probably producing cancer cells all the time,” Dr. Brewer says. “But your immune system gobbles them up and gets rid of them. Extreme stress and other ailments that decrease your immune function may put you at greater risk of cancer.”

Are All Tumors Dangerous?

No. As mentioned above, some tumors are benign and some are malignant. The cells in benign tumors won’t spread to other parts of the body. They can be removed, and in most cases, won’t grow back. Even some malignant tumors won’t actually make you sick (more on this below).

Does All Cancer Need to be Treated?

In some cases, the best approach to a diagnosis of cancer may be to monitor it but not treat it, at least not right away.

Knowing that not all cancers need to be treated with medication, chemotherapy, radiation or surgery is important to understanding the disease and dealing with a diagnosis. Many experts are concerned, in fact, that cancer is actually being over-treated with invasive therapies and procedures simply because we (wrongly) assume that all cancers will kill us. In 2013, a group at the National Cancer Institute recommended that low-risk cancers be renamed IDLE (indolent lesions of epithelial origin) conditions—meaning slow-moving—instead of cancer as a way to reduce unnecessary treatments. These cancers include some types that affect the breasts, prostate, thyroid and lungs.

Not getting treated, though, isn’t the same as doing nothing. Sometimes the best medical approach is what’s called “active surveillance,” meaning your doctor monitors you on a regular basis in case your abnormal cells do turn into a cancer that needs treatment. The benefit is that you avoid treatments such as chemotherapy or surgery unless you actually need them.

What Are the Most Common Cancers?

The 10 most common cancers are breast, prostate, lung, colorectal (colon and rectal), melanoma, bladder, non-Hodgkin lymphoma, kidney, thyroid, endometrial, leukemia and pancreatic. It’s worth mentioning that this list doesn’t include non-melanoma kinds of skin cancer, which are common but almost never fatal.

What Are the Most Dangerous Types?

Death rates from cancer have been declining steadily since the early 1990s. Some cancers, such as those of the pancreas and lungs, still have a poorer prognosis than others, though. Ovarian cancers have a high mortality rate, too, because they are difficult to diagnose at an early stage.

The earlier a potentially deadly cancer can be found, the better your chances. Cervical cancer has a high survival rate, in large part because regular Pap smears can detect it at a very early, often precancerous, stage. And many cases of colon cancer are prevented because colonoscopies can remove precancerous polyps (abnormal growths) before they become cancer.

When it comes to breast cancer, a lot depends on the type: The survival rate of ductal carcinoma in situ, in which abnormal cells are confined to a milk duct in the breast, is about 100 percent for five years, for example, but invasive breast cancer can be fatal. Prostate cancer survival also depends on whether the cancer is slow-growing or aggressive.

Each person is unique, and each cancer diagnosis is individual. Detecting cancer early can often greatly increase the success of treatment, so a “dangerous” cancer that’s caught early may have a better outcome than a less “dangerous” one that isn’t diagnosed until a much later stage.

How Can I Reduce My Cancer Risk?

Smoking is responsible for nearly one-third of all cancers, so not smoking (or quitting smoking) is the single best way to prevent cancer. A healthy diet rich in vegetables, fruits and whole grains, with only small amounts of meat (or none), refined grains and added sugar, may also help protect against many types. So does maintaining a healthy weight and being physically active.

“Exercising is such a big way to help prevent cancer,” Dr. Brewer says. “If you are physically active, you lower your risk of obesity, which affects breast, esophageal and colorectal cancers. Exercise also decreases inflammation on a continual basis, which also reduces your cancer risk.”

Other factors you can control that may lower your risk of developing cancer include drinking alcohol moderately (if at all) and protecting yourself from environmental toxins—through clean eating that’s as free of pesticides and other chemicals as possible, for example. Controlling stress is also important. Although stress doesn’t appear to cause cancer directly, it may accelerate the growth and spread of tumors and keep your immune system from functioning at capacity. “When I talk to people who have a strong family history of cancer, I talk about mitigating stress to improve your immune system,” adds Dr. Brewer.

The general advice about screenings has been to get them regularly to detect cancers as early as possible. However, screenings such as those for breast, prostate and cervical cancer can also catch precancerous cells and tumors that may not cause harm in a person’s lifetime; this can lead to anxiety and unnecessary invasive treatments. In some cases, the screenings themselves—like biopsies for prostate cancer—can cause side effects.

Here’s what you need to know: No one is arguing that screenings for cancer are unnecessary and should be eliminated. The questions to ask your doctor are: the age at which you should start screenings; how often you should get each kind; and the age at which you can stop. The official recommendations are typically for the general population, not your individual case, so they can’t take into account your family history, health status and lifestyle, as well as your personal perspective on what’s worth a risk and what’s not. Based on all of these factors, your doctor will recommend screenings on a schedule that makes sense for you.

“Remember that only five to 10 percent of cancers are hereditary and, therefore, over 90 percent are not,” Dr. Brewer says. “This means that even if you do not have a family history of cancer, you still need to have cancer screenings to pick up those cancers that are potentially at an early treatable stage.”

Reference(s)

American Cancer Society

Centers for Disease Control and Prevention

Fred Hutchinson Cancer Research Center

The Journal of the American Medical Association (August 2013)

Mayo Clinic

National Cancer Institute

U.S. National Library of Medicine

About the author

Bob Barnett is a New York City-based health journalist, editor and book author who has been writing about nutrition, fitness, psychology and lifestyle medicine for more than 20 years.